[ci skip] remove markdown from issue template (#6705)

Some areas of the issue template will not render markdown

.github/ISSUE_TEMPLATE/config.yml

@@ -7,4 +7,4 @@ contact_links:
     url: https://discord.gg/papermc
     about: |
       Due to GitHub not currently allowing private issues, exploit reports are currently handled via our Discord.
-      To report an exploit, see the `#paper-exploit-report` channel.
+      To report an exploit, see the #paper-exploit-report channel.